Process for the detection of marked components of a composite article using infrared blockers

ABSTRACT

Disclosed is a process for the detection of marked components of a composite article. The present invention relates to detecting the presence, position, concentration and/or distribution of one or more components in a composite article, and to registration inspection of a composite article using infrared radiation. In one embodiment of the invention, infrared blockers, such as absorbing infrared blockers, are incorporated into the component of interest in the composite to increase the visibility of the marked component during inspection.

This application claims the benefit of provisional application Ser. No.60/362,833, filed Mar. 9, 2002, application Ser. No. 60/372,866, filedMar. 9, 2002, provisional application Ser. No. 10/094,404, filed Mar. 9,2002, provisional application Ser. No. 60/364,264, filed Mar. 14, 2002,provisional application Ser. No. 60/364,329, filed Mar. 14, 2002, and ofprovisional application Ser. No. 60/382,812, filed May 23, 2002, all ofwhich are hereby incorporated by reference in their entirety for allpurposes.

FIELD OF THE INVENTION

The present invention relates to detecting the presence, position,concentration and/or distribution of one or more components in acomposite article, and to registration inspection of a compositearticle, using infrared radiation and infrared detectors in conjunctionwith the addition of an infrared blocker to the components.

BACKGROUND OF THE INVENTION

A vast number of applications exist in which it is necessary ordesirable to monitor the presence and/or position of one or morecomponents of a composite article during manufacturing. For instance, ina largely automated process for manufacturing disposable absorbentproducts such as diapers and other incontinence products, certaincomponents (e.g., support layers, absorbent pads, elastic components,fastener components, etc.) must be positioned or aligned with respect toeach other and/or other components in order to produce an acceptableproduct. Accordingly, inspection systems are commonly used to detect thepositions of such components during manufacturing. If an inspectionsystem determines that one or more components are out of position andthus do not properly register with other components, the inspectionsystem typically outputs one or more signals indicating that certainarticles should be culled and discarded, that the process should beadjusted so as to bring out-of-position components into proper position,that the process should be adjusted so that subsequent components arebrought into proper registration with one another, etc.

An exemplary registration inspection system is disclosed in U.S. Pat.No. 5,359,525, the disclosure of which is incorporated herein byreference. As described therein, registration inspection of a compositearticle undergoing fabrication is accomplished by producing an image ofthe article and then analyzing the image to detect the position of oneor more components. The detected positions are then compared to idealpositions to thereby determine whether the one or more components areproperly positioned. This registration inspection system employsconventional video cameras for capturing visible and ultraviolet lightreflected by and/or transmitted through components in order to producestill video images of such components. Thus, after producing a videoimage of a composite article and its several components, the image canbe analyzed to determine whether the components are properly positionedand registered with one another.

Although highly useful for many applications, the inventors hereof havedetermined that the inspection system disclosed in the aforementionedpatent, and similar systems, have certain shortcomings. For example,such systems are not well suited for determining the presence and/orpositions of components underlying other components which aresubstantially opaque to visible and/or ultraviolet light. Additionally,such systems are not well suited to determining the presence and/orpositions of components which tend to scatter visible and ultravioletlight.

Another exemplary inspection system, disclosed in U.S. Pat. No.6,224,699, employs infrared detectors for producing infrared images ofproducts undergoing formation by sensing infrared radiation emitted byheated product components. The produced images are then compared withreference information to determine, for example, whether the productcomponents are properly positioned. However, this system is not wellsuited to detecting product components which have cooled, or which werenever heated in the first instance.

The inventors hereof have also recognized that prior art inspectionsystems and processes are not well suited to detecting the distributionand/or concentration level (e.g., quantity) of certain productcomponents.

SUMMARY OF THE INVENTION

In order to solve these and other needs in the art, the inventors hereofhave succeeded at designing processes and systems for detecting thepresence, position, distribution and/or concentration of one or morecomponents in a composite article, including adjacent components,overlapping components, and components which overlie or underlie othercomponents, including components which are disposed or sandwichedbetween other components. The present invention also relates tocomposite articles produced or inspected using such processes andsystems. The invention is especially well suited to detecting propertiesof disposable absorbent articles undergoing fabrication and/or qualityinspection, although the invention is far from so limited, as will beapparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of a process for detecting whether one or morecomponents are properly positioned in a composite article according toone preferred embodiment of the present invention.

FIG. 2 is a block diagram of an exemplary system for implementingvarious aspects of the present invention, including the process of FIG.1, where a composite article is positioned between an infrared detectorand a radiation source.

FIGS. 3(a) and 3(b) are side and top views of an exemplary compositearticle.

FIG. 3(c) illustrates an image of the composite article of FIGS. 3(a)and 3(b) produced using the system of FIG. 2.

FIG. 4 is a block diagram of another exemplary system for implementingvarious aspects of the present invention, including the process of FIG.1, where the infrared detector and radiation sources are positioned onthe same side of the composite article.

FIG. 5 is a top view of an exemplary disposable training pant havingoverlapping side panels.

FIG. 6 is a sectional view taken along line 6—6 of FIG. 5, illustratingthe training pant of FIG. 5 positioned over an infrared radiationapparatus.

FIG. 7 illustrates an image of the training pant of FIG. 5 producedusing the system of FIG. 2.

FIG. 8 illustrates Equation B (as further described herein), showingrelative light scattering under identical conditions as a function ofwavelength.

FIG. 9 illustrates Equations C1 and C2, showing the ratio of scatteredto incident light (l_(s)/l_(o)) as a function of the average lightscattering particle radius (in microns) for a nominal set of conditions.

Corresponding reference characters indicate corresponding featuresthroughout the several views of the drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A. Infrared Registration Inspection System

A process of detecting whether one or more components are properlypositioned in a composite article is illustrated in FIG. 1 and indicatedgenerally by reference character 100. The process 100 includesirradiating the composite article with infrared radiation as shown inblock 102 of FIG. 1, and producing an image from infrared radiationreceived from the irradiated composite article, as shown in block 104.The process further includes, in block 106, identifying a position of avariation in the produced image corresponding to an edge position of acomponent in the composite article. In block 108, the position of thevariation identified in the produced image (in block 106) is comparedwith reference data to thereby determine whether the component of thecomposite article is properly positioned therein. By utilizing infraredradiation rather than (or in addition to) visible light, the process 100cannot only detect the position of components which tend to scattervisible and ultraviolet light, including components which overlie othercomponents, but also the position of components which underlie othercomponents, including components disposed or sandwiched betweencomponents which are substantially opaque to visible and ultravioletlight, as further explained below.

One exemplary system 200 for implementing the process 100 of FIG. 1 (andother aspects of the present invention) is illustrated in FIG. 2. Asshown therein, the system 200 includes an infrared radiation source 202for irradiating a composite article 204 with infrared radiation. Thesystem 200 further includes an infrared detector 205 for producing, inthis example, a two dimensional image from infrared radiation 206transmitted through the composite article 204. The infrared detector 205is operatively connected to an image analyzer 208, which itself isoperatively connected to a comparator 210.

The arrows in FIG. 2 are intended to represent constant or intermittent(e.g., periodic) movement of the composite article relative to thesystem 200. In one embodiment, the composite article is moved into afield of view of the infrared detector 205 for inspection. Alternatively(or additionally), the infrared detector 205 may be moved (or havecomponents which are moved, such as in a scanning motion) for inspectionof the composite article.

The infrared radiation source 202 may emit infrared radiation (i.e.,radiation having a wavelength between about 700 nanometers and 1millimeter) continuously or intermittently. If the radiation source 202emits continuously, the detector 205 may be shuttered (electronically orotherwise) to prevent blurring of the image due to high speed movementof the composite article, if applicable. If the radiation source emitsradiation intermittently, the detector is preferably synchronized withthe radiation source so as to produce an image contemporaneously withthe irradiating of the composite article.

The image analyzer 208 is configured to receive the image produced bythe infrared detector 205. This image will include variations thereinwhich correspond to variations in radiation levels (and/or wavelengths)received by the infrared detector from a top side of the compositearticle 204. In one embodiment, the image produced by the infrareddetector 205 is a black-and-white image in which radiation levelvariations are depicted in varying grayscale levels. Alternatively, suchvariations may be depicted in the image in another manner, such as inthe form of color variations. Regardless of their form, the imageanalyzer 208 is preferably configured to identifying the position of oneor more variations in the produced image each corresponding to an edgeposition of a component in the composite article. These identifiedpositions are then compared by the comparator 210 with reference data(e.g., ideal or predetermined position data) to determine whether thepositions of components in the composite article are acceptable. Forexample, the comparator may determine whether the edge position of aparticular component is precisely where it is supposed to be, or whetherit falls within a predetermined range of acceptable positions.

The image analyzer can be configured to determine the positions ofvariations in the image produced by the infrared detector, and thus theedge positions of components in the composite article, either as fixedpositions or relative positions, or a combination of both. Thus, theimage analyzer may determine the edge position of a composite articlecomponent relative to a fixed point, edge or region of or in the image,relative to another component or the edge of another component in theimage, relative to a registration mark on or about a component of thecomposite article, etc. As one example, the image analyzer may firstdetermine the edge position of a first component as a fixed position(e.g., in terms of x,y coordinates or, in the case of a threedimensional image, in terms of x,y,z coordinates), and then determinethe edge position of a second component (or another edge position of thefirst component) relative to the previously determined edge position ofthe first component.

The comparator is preferably configured to compare positions identifiedby the image analyzer with reference data (e.g., predetermined fixedand/or relative position data, as applicable) to thereby determinewhether one or more components are properly positioned in the compositearticle. Depending on the outcome of such comparison(s), the comparatormay output one or more signals to a process controller indicating thatone or more composite articles should be culled and discarded, that theprocess should be adjusted so as to bring out-of-position componentsinto proper position, that the process should be adjusted so thatsubsequent components are brought into proper registration with oneanother, etc. The comparator may also sound an operator alarm (such asan audible alarm) upon determining that one or more components of acomposite article, or a series of composite articles, are mispositioned,and may display an image of the composite article or the componentsthereof to an operator for monitoring, tracking or diagnostic purposes.

FIGS. 3(a) and 3(b) illustrate a composite article 300 which representsjust one possible configuration of the composite article 200 shown inFIG. 2. As best shown in FIG. 3(a), the composite article 300 includesan upper component 302 and a lower component 304 which underlies aportion of the upper component 302. As shown in FIG. 3(b), the uppercomponent 302 includes an edge 306, and the lower component 304 includesan edge 308. In this embodiment, both the upper component 302 and thelower component 304 partially inhibit infrared radiation from passingtherethrough (e.g., by absorbing and/or reflecting some of suchradiation). FIG. 3(c) illustrates an exemplary two dimensionalblack-and-white image 310 of the composite article 300 as produced bythe system 200 of FIG. 2. In this example, darker regions of the image310 correspond to portions of the composite article 300 from which theinfrared detector received relatively less infrared radiation. Thus, aposition of one contrast variation (i.e., from light to medium) 312 inthe image 310 represents a position of the upper component's edge 306.Similarly, a position of another contrast variation (i.e., from mediumto dark) 314 in the image 310 represents a position of the lowercomponent's edge 308. In fact, the entire boundary of the lowercomponent 304 is readily apparent in the image 310 of FIG. 3(c).

The lower component 304 appears darker in the image 310 than thoseportions of the upper component which do not overlie the lower componentsince the infrared radiation which passes through the lower component304 is partially absorbed or reflected by the upper component 302. Inother words, the upper component and the lower component provide acumulative absorptive and/or reflective effect in those regions wherethe upper component overlies the lower component. Therefore, theinfrared detector receives less infrared radiation from that portion ofthe upper component which overlies the lower component than it does fromsurrounding portions of the upper component (assuming all portions ofthe upper component uniformly inhibit the same amount of infraredradiation from passing therethrough, although this is not a requirementof the invention).

By processing the image 310 of FIG. 3(c), the image analyzer 208 canidentify positions of the aforementioned variations and thus provideidentified position data to the comparator 210. In one embodiment, eachpixel or element of the image 310 is assigned a grayscale value of0-255, where higher grayscale values represent areas from whichrelatively less infrared radiation was received by the infrareddetector. The image analyzer identifies predefined variations in thesegrayscale values which correspond to the component positions. Thecomparator then compares this position data with predefined positiondata to determine whether the upper component and the lower componentare properly positioned in an absolute sense and/or with respect to oneanother, and output appropriate signals to the process controller.

In the embodiment described immediately above, both the upper component302 and the lower component 304 partially inhibited infrared radiationfrom passing therethrough (e.g., by absorbing and/or reflecting suchradiation). As should be apparent, the lower component could besimilarly detected through the upper component if the lower componentprevents all infrared radiation incident thereon from passingtherethrough.

B. Infrared Blockers

In accordance with one aspect of the infrared detection system for theinspection of composite articles described herein, the degree to whichone or more components of the composite article absorbs or reflectsinfrared radiation, and hence the degree to which the component can bedetected by the infrared system, can be significantly increased byintroducing one or more marking compounds, such as “infrared blockers”or “infrared markers,” into the component or components of interest in acomposite product. Infrared blockers have the capacity to absorb(absorbing infrared blockers) or reflect (reflecting infrared blockers)infrared light over a pre-specified wavelength range determined by acombination of the emission source output wavelength, the range ofsensitivity of a detector, and the specific blocker. The infraredblockers are introduced into or onto the desired component prior toinspection of the composite product with the infrared detection systemdescribed herein, and can be applied to the component(s) in the form ofdyes, films, tags, paints, other coatings, etc., as further discussedherein. The introduction of such infrared blockers can significantlyincrease the absorbence or reflectance of the component of interest inthe composite product resulting in an improved image which can moreprecisely detect and pinpoint the cross direction and/or machinedirection position of one or more components of the composite article.

1. Absorbing Infrared Blockers

When absorbing infrared blockers are utilized in one or more componentsof the composite article being inspected, a back lighting geometry istypically utilized wherein the light emitted from any number of infraredsources is significantly absorbed at either specific or broad wavelengthregions so that it cannot reach the detector which is located on theopposite side of the source. A suitable geometry setup for usingabsorbing infrared blockers is shown in FIG. 2. Although less preferred,other lighting geometries known to those skilled in the art can beutilized in accordance with the present invention in combination withabsorbing infrared blockers.

Absorbing infrared blockers suitable for use in the present inventioninclude high absorption coefficient infrared absorbing dyes, highlyabsorbing materials such as filters and dielectrics capable ofselectively absorbing light, or dark materials which absorb a broad bandof light.

A list of filter types which could be used to block specific wavelengthsof light include dielectric interference filters made from films,neutral density filters, colored films, high-pass and low-pass films,edge reflective films, and other films containing dyes or light-blockingmaterials. For dielectric filter interference, filters are designed totransmit light for only a defined spectral bandpass, conversely they areused for blocking light over adjacent bands. These filters are comprisedof a solid Fabry-Perot cavity. Interference films can be made by asandwich of two partially reflective metallic film layers and areseparated by a transparent dielectric spacer film layer. The partiallyreflective layers are made of higher refractive index than thedielectric spacer layer and have a thickness close to one-fourth thedesired transmittance peak wavelength. The lower refractive index spacerlayer is made to a thickness of one-half the desired transmittance peakwavelength. The thickness of the dielectric spacer layer determines theactual peak transmission wavelength for the filter. The actualwavelength position of the transmittance peak through a Fabry-Perot,interferometer based, interference filter is given as:λ_(M)=2×n _(s) t _(s) cos θ/iwhere λ_(M) is the wavelength of maximum transmittance for theinterference filter composite (in micrometers), n_(s) is the refractiveindex of the dielectric spacer, t_(s) is the thickness of the dielectricspacer in micrometers, θ is the angle of incidence of the lightimpinging onto the dielectric spacer, and i is the nonzero integerorder-number for the interference as (1, 2, 3, 4, . . . n). Thewavelength of peak transmittance for an interference filter can be movedby varying the angle of incidence (θ) of collimated light onto thesurface of the filter. The relationship defining the peak position ofmaximum transmission is given as:λ_(M)=λ_(M){1−(n _(A) /n _(S)}^(1/2)sin^(2θ)where λ_(M) is the wavelength of the new peak transmission position atan incidence angle greater than 0 degrees, λ_(M) is the wavelength ofmaximum transmittance for the interference filter composite (inmicrometers) from the previous equation, n_(A) is the refractive indexof the surrounding medium (air=1.0003), n_(S) is the refractive index ofthe dielectric spacer, and θ is the angle of incidence of the lightimpinging onto the dielectric spacer. The technology for making thesefilters is well-known and has been described in multiple references forglass substrates. The conventional materials are commercially availableas per specifications from such suppliers as Melles Griot and EdmundScientific. Films are described in U.S. Pat. No. 3,711,176, U.S. Pat.No. 5,103,337, and WO 96/19346, and WO 97/17303. Similar films arecommercially available through Edmund Scientific and other commercialoptical suppliers. For this present invention the material structure tobe registered is laminated with the dielectric-based film acting as aninterference filter. The wavelength selected for measurementillumination must be attenuated by the bulk of the manufacturedstructure while the structure to be registered transmits more light andthus is lighter colored to provide the registration profile.

Dark materials suitable for use in the present invention are thosematerials with an optical density difference of at least 1.0 as comparedto the surrounding media. The optical density (O.D._(T)) value fortransmittance is given as:O.D. _(T)=log₁₀(100/T _(p))where O.D._(T) is the optical density of a material at a specificwavelength, and T_(p) is the percent transmittance of the material at aspecific wavelength.

Particularly preferred absorbing infrared blockers for use in thepresent invention are high absorption coefficient infrared absorbingdyes. Generally speaking, absorbing infrared blockers are selected foruse in the present invention based on their safety, cost efficiency andhigh extinction coefficient (i.e., absorptivity) for their intended use.Preferred dyes are typically selected based on a combination of factorsincluding: (1) safety issues relative to exposure limits; (2) highabsorptivity; (3) solubility; (4) center wavelength of maximum blockingor optical absorbence; and (5) full width at half-maximum bandwidth. Themost useful dyes preferably do not contain antimony, nickel, or otherheavy metals represented on the periodic table as Period 4, Groups IIIAthrough VIB, and Period 5, Groups IA through VIB due to safety anddisposal issues. Preferred dyes contain a majority of the elementscarbon, hydrogen, and oxygen, with nitrogen, sodium, and chlorinetypically permitted in low molar concentrations, preferably less than 10percent mole fraction for each element.

Suitable absorbing infrared blockers for use in the present inventiondesirably have an absorption peak maximum within the range of from about750 nm to about 1200 nm, more desirably from about 750 nm to about 1150nm, and still more desirably from about 775 nm to about 1050 nm.Further, the absorbing infrared blockers desirably have an extinctioncoefficient within the range of from about 1×10⁴ L/mole cm to about5×10⁵ L/mole cm or more, and more desirably from about 5×10⁴ L/mole cmto about 3×10⁵ L/mole cm or more, and most desirably, the extinctioncoefficient will be about 1.5×10⁵ L/mole cm or more. In this regard itis to be noted that essentially no upper limit to the extinctioncoefficient applies, and that safe materials having higherabsorptivities are preferred, as materials with higher absorptivitiesincrease the contrast in the resulting visual image, allowing forincreased detection.

Various types of absorbing infrared dyes are suitable for use in thepresent invention including, for example, solvent soluble absorbinginfrared dyes, water soluble absorbing infrared dyes, and metal complexabsorbing infrared dyes. Solvent soluble absorbing infrared dyes aretypically soluble in chloroform and petroleum ether, as well as othernon-polar organic solvents. Water soluble absorbing infrared dyes aresoluble in water, as well as alcohols and glycols. Suitable solventsoluble and water soluble absorbing infrared blockers for use with thecomposite components described herein can have the empirical formulasshown in (I) and (II), respectively:C_(x)H_(y)N_(z)(R¹)_(w)(R²)_(v)  (I)C_(x)H_(y)N_(z)(R¹)_(w)(R²)_(v)(R³)  (II)wherein x is a whole number from 30 to 70, preferably from 32 to 62, yis a whole number from 32 to 112, preferably from 36 to 96, z is a wholenumber from 0 to 6, R¹ is selected from the group consisting of Cl, O,and Sb, wherein w and v are whole numbers from 1 to 12, R² is I or Owhen R¹ is Cl, S when R¹ is O, and F when R¹ is Sb, and R³ is selectedfrom the group consisting of F and S. Some water soluble forms of theblocking compounds described herein may be in the form of a salt having,for example, a sodium or potassium cation.

Examples of solvent soluble absorbing infrared dyes commerciallyavailable from American Dye Source, Inc., and suitable for use in thepresent invention include, but are not limited to those shown in Table1:

TABLE 1 Catalog No. Wavelength (nm) Chemical Formula ADS775MI 775C₃₂H₃₆ClN₂I ADS775MP 775 C₃₂H₃₆ClN₂O₄ ADS775HI 780 C₄₄H₆₀ClN₂I ADS775PI780 C₃₆H₄₄ClN₂I ADS775PP 780 C₃₆H₄₄Cl₂N₂O₄ ADS780MP 780 C₃₁H₃₄Cl₂N₂O₄ADS780HO 780 C₃₄H₄₀N₂O₆C₁₂ ADS800AT 798 C₅₄H₅₄N₂O₄S ADS805PI 805C₃₅H₄₂ClN₂I ADS805PP 803 C₃₅H₄₂Cl₂N₂O₄ ADS805PA 803 C₃₁H₃₄Cl₂N₂O₄ADS805PF 803 C₃₇H₄₂F₃ClN₂O₂ ADS812MI 812 C₄₀H₄₀ClN₂I ADS815EI 815C₄₂H₄₄ClN₂I ADS818HI 818 C₅₂H₆₄ClN₂I ADS818HT 818 C₅₉H₇₁Cl₂N₂SO₃ADS822MT 822 C₅₃H₅₂N₂O₃S₂ ADS830AT 813 C₄₇H₄₇ClN₂O₃S ADS838MT 838C₄₆H₄₅ClN₂O₃S ADS840MT 841 C₃₇H₃₅ClN₂O₃S ADS845BI 845 C₃₆H₄₀ClN₂IADS905AM 905 C₆₂H₉₆N₆SbF₆ ADS956B1 956 C₃₆H₄₀Cl₂N₂O₄ ADS104OP 1046C₅₅H₅₄ClO₆ ADS1045P 1048 C₄₇H₃₉ClO₆ ADS1050P 1048 C₄₉H₄₂ClO₆ ADS1060A1060 C₆₂H₉₂N₆Sb₂F₁₂ ADS1065A 1060 C₆₂H₉₂N₆Sb₂F₁₂ ADS1120P 1120C₅₂H₄₄Cl₂O₆

Examples of water soluble absorbing infrared dyes commercially availablefrom American Dye Source, Inc., and suitable for use in the presentinvention include, but are not limited to, those shown in Table 2:

TABLE 2 Catalog No. Absorption Chemical Formula ADS780WS 781C₃₈H₄₆ClN₂O₆S₂Na ADS785WS 785 C₄₃H₄₇N₂O₆S₂Na ADS790WS 791 C₄₄H₅₂N₃O₆S₃NaADS805WS 807 C₃₆H₄₄ClN₂O₆S₂Na ADS820WS 820 C₄₂H₄₉N₂O₆S₃Na ADS830WS 822C₄₆H₅₁ClN₂O₆S₂Na ADS850WS 844 C₄₅H₄₈ClN₂O₆S₂Na

Additionally, metal-based metal complex absorbing infrared dyes can beutilized in accordance with the present invention. Suitable metalcomplex absorbing infrared blockers for use in the present inventioncommercially available from American Dye Source, Inc. include, but arenot limited to, those shown in Table 3:

TABLE 3 Catalog No. Absorption (nm) Chemical Formula ADS845MC 845C₂₈H₄₀Cl₄NS₄Ni ADS870MC 867 C₂₈H₃₈Cl₆NS₄Ni ADS880MC 882 C₃₂H₂₈S₄NiADS885MC 885 C₃₂H₂₆O₄S₄Cl₂Ni ADS890MC 892 C₃₀H₄₈NS₄Ni ADS920MC 922C₃₂H₂₈O₄S₄Ni ADS990MC 990 C₃₂H₃₀N₂N₄Ni

Suitable absorbing infrared dyes for use in the present inventiontypically have molecular weights ranging from about 450 g/mol to about1450 g/mol, and desirably from about 600 g/mol to about 825 g/mol. Themolecular weight of the dye may be an important consideration relativeto its dispersibility and solubility for adding to the polymer films.The colors of absorbing infrared blockers range from light gray to darkgreen, the lighter colors having high absorptivity values being moredesirable.

Generally, the absorbing infrared blockers are added to the desiredcomponent of the composite article in an amount sufficient to increasethe detectability of the desired component in the infrared inspectionsystem described herein relative to other components in the compositearticle. Typically, the absorbing infrared blockers can be added tomaterials for registration by introducing the blocking compounds intothe particular component at a concentration of at least about 10 partsper billion and more desirably at a concentration of at least about 10parts per million. In certain circumstances where the desired absorbinginfrared blocker has a relatively low absorptivity, the blocker can beadded at a level of up to about 10% (weight/weight). In most cases, aconcentration of absorbing infrared blocker from about 10 parts permillion up to about 1% or 2% (weight/weight) is sufficient to impart thedesired benefits on the treated component.

In accordance with the present invention, there are several methods thatcan be utilized to introduce the absorbing infrared blocker, such as anabsorbing infrared dye, into or onto a component of a composite productto improve the detectability of the component as compared to otheruntreated components of the article. It will be recognized by oneskilled in the art that one or more absorbing infrared blockers can beintroduced into one or more components of the composite article.

In one method, the absorbing infrared blockers described herein for usein the present invention can be introduced into the desired component ofthe composite material by pre-mixing the blocker directly into a polymerfor molding or extrusion into various plastic structures or films foruse in a composite article. In this embodiment, the blocker is addeddirectly into the polymer and the mixture is agitated to blend theblocker prior to the polymer/blocker mixture being molded or extrudedinto a structure or film. Once the polymer/blocker mixture is molded orextruded into a desired component, the blocker is contained within thecomponent and can improve detectability of the component as describedherein through increased absorption of infrared radiation.

In an alternative embodiment, the absorbing infrared blockers can firstbe mixed with a solvent and dissolved therein, and then the solutionintroduced into a polymer for molding or extrusion. In this embodiment,the solvent/absorbent blocker solution is typically continuouslyagitated throughout the molding or extrusion process to ensure that thesolution is homogeneous and the amount of settling out of the blocker,if any, during molding is minimized. During molding or extruding, thesolvent part of the solution is typically evaporated off, resulting in acomponent containing the desired blocker. In a related embodiment, theblocker can be batch-mixed with an adhesive or ointment which isultimately introduced onto a component of the composite product. Thisembodiment allows for registration of the adhesive or ointment relativeto one or more other components.

Regardless of whether the absorbing infrared blocker is added directlyto the polymer, or added to the polymer as a solution containing asolvent, the blockers are preferably stable at extrusion temperatures offrom about 70° C. to about 300° C. Additionally, the blockers arepreferably efficacious and substantially chemically stable throughoutthe time of manufacture up to and including 15 days beyond the storageand manufacturing use time.

In a further alternative embodiment, the absorbing infrared blockers canbe made into a paint or coating compound and introduced onto any surfacelayer of a single or composite polymer film or structure. In thisembodiment, the blocker is typically mixed with a carrier compound andintroduced or painted directly onto a component and allowed to dry priorto the component being inspected as described herein. Similarly, theblockers described herein can be blended into a printable ink for use inprinting specific patterns onto polymer films and structures.

In a further alternative embodiment, the absorbing infrared blockers canbe combined with a carrier resin such as a linear low densitypolyethylene or polypropylene and the mixture heated and melted tocreate a solution comprising the absorbing infrared blocker. Thissolution or hot melt can then be applied directly onto the desiredcomponent of the composite article to introduce the blocker onto thecomponent. The amount of blocker and carrier resin used to create thehot melt can vary depending upon the desired concentration of blockerresulting on the component.

Alternatively, the infrared blockers can be printed directly into oronto a component of a composite product, or can be applied in a liquidor powder form from a feeder or sprayer. One skilled in the art willrecognize that there are other methods that could be utilized tointroduce the infrared blockers described herein into or onto one ormore components of a composite article to achieve the intended benefits.As such, the examples of various methods included herein should be takenas illustrative and not as limiting in any manner.

Regardless of the manner in which the absorbing infrared blockers areintroduced into or onto the component of the composite article, theblocker is preferably substantially chemically non-reactive with thepolymers, polymer additives, adhesives, and polymer coatings. Further,it is preferable that the blockers not bleed out or migrate from thecomponents in which they are introduced, as this may result in a lessdetectable component.

2. Reflecting Infrared Blockers

Alternatively, reflecting infrared blockers can be utilized inaccordance with the present invention to improve the detectability ofone or more components of a composite article. When reflecting infraredblockers are utilized in one or more components of the composition beinginspected, a gloss image can be used for registration by detecting thereflected image from the surface of the viewed object. This opticalgeometry is accomplished by positioning the infrared source and thedetector on the same side of the viewed object. The angle ofillumination and detection between the source and the detector relativeto the viewed object is from about zero degrees to about 90 degrees, andpreferably is about 45 degrees to allow for maximum detectability. Theincident light is reflected from the reflecting blocker surface anddetected at preferably a 45 degree angle as this angle reduces theglossy surface reflection of the object relative to the reflection ofthe infrared blocker. A suitable setup for using reflecting infraredblockers is shown in FIG. 4.

In one embodiment utilizing reflecting infrared blockers, infrared lightcan be reflected off of one or more components of a composite articleduring registration utilizing multilayer reflective films which providelight reflectance characteristics over a broad and pre-specified rangeof wavelengths, as discussed below. By varying the optical thickness ofa sandwich of two or more layers of optically active films, a multilayerreflective film can be designed that reflects light over a broad band ofwavelengths. This band is often referred to as the reflection band, orstop band. Such multilayer reflective films comprising alternatinglayers of two or more polymers to reflect light are described in, forexample: Wheatley et al. (PCT Application Nos. WO 99/36809 and99/36810); Alfrey, Jr. et al. (U.S. Pat. No. 3,711,176); Schrenk et al.(U.S. Pat. No. 5,103,337); Jonza et al. (PCT Application No. WO96/19347); and, Ouderkirk et al. (PCT Application No. WO 95/17303); allof which are incorporated herein by reference.

The reflection and transmission spectra of a particular multilayer filmdepend primarily on the optical thickness of the individual layers.Optical thickness may be defined as the product of the actual thicknessof a layer times its refractive index. By using this relationship,suitable multilayer films can be designed to reflect infrared light, aswell as visible and ultraviolet light, by choosing the appropriateoptical thickness of the layers in accordance with the previouslyreferenced art, as described using Equation (A):Wavelength_(I)=(2/I)*T _(R)  (A)wherein I is an integer representing the particular order of thereflected light (as 0, 1, 2, etc.), and T_(R) is the thickness of anoptical repeating unit (also called a multilayer stack), consisting oftwo or more polymer layers, T_(R) is always one-half wavelength inthickness, where wavelength is the first order reflection peak. Byvarying the optical thickness of an optical repeating unit within amultilayer film structure, a multilayer film can be designed to reflectlight over a specific wavelength region such that the resultingmultilayer reflective film can be used in a composite article forregistration.

Wavelength regions are typically shortwave near infrared or fromapproximately 690 to 1200 nanometers (0.69 to 1.2 microns), preferably750 to 1100 nanometers (0.75 to 1.1 microns). Wavelength regions aboveand below this region could also be utilized in a less preferredembodiment; especially 0.69 microns to 2.5 microns. Although this lesspreferred region can be utilized in accordance with the presentinvention, it is typically less preferred as detection systems for thisregion are typically expensive.

Although utilizing multilayered films is within the scope of the presentinvention, it is typically less preferred than blocking dyes orscattering approaches discussed herein due to the complexity and cost ofthe multilayered film construction. Suitable materials are commerciallyavailable, but cost considerations for mass production must beconsidered prior to use. Most commercially available materials areconstructed specifically for desired center wavelength of lighttransmission, bandwidth of light transmitted, and cost. The thicknessand number of layers for the construction of these films is determinedby these performance specifications. Typically, multilayeredinterference films are made using a glass or quartz substrate. However,polymer film-based filters could be laminated into the registrationstructures using adhesives or other forms or bonding such as precisionthermal annealing or ultrasonic bonding.

In an alternative embodiment, particle light scattering compounds can beutilized to create the desired infrared radiation reflectance to improvecomponent detectability. In particle light scattering, such as what isreferred to as Rayleigh scattered light, the intensity of the scatteredenergy (I_(RS)) is inversely proportional to the 4th power of theincident light energy (λ), as given by Equation (B) and illustrated inFIG. 8.I _(RS)∝1/λ⁴  (B)

Typically, the optimum wavelengths of light for utilizing the particlelight scattering phenomenon are those below about 1150 nanometers,preferably below about 950 nanometers, and preferably from about 750 toabout 850 nanometers. However, the longer near infrared wavelengthsabove 950 nm are also useable, even though they demonstrate lowerrelative intensity, and are therefor less preferred.

A scattering reflection technology can be based upon the optical physicsmodeled by the relationship:I _(s) /I _(o)=1/r ²*(2Π/λ)⁴*α²sin²θ  (C1)

wherein

-   -   I_(s) is the scattered or reflected light;    -   I_(o) is the total incident light intensity;    -   r is the average particle radius;    -   λ is the wavelength of the incident radiation;    -   θ is the reflected light angle, assuming the incident energy is        normal to the viewed surface of an object; and,    -   α is a proportionality factor, given as α=n²−1/4Πd, where n is        the refractive index of the particles scattering or reflecting        light and d is the particle density in numbers of particles per        cubic cm (cm⁻³).

Highly reflective particles, typically defined as particles with anextremely low reflection extinction coefficient (i.e., highreflectivity) for the wavelength region of interest, such as awavelength of less than about 950 nanometers, preferably less than about850 nanometers, and more preferably less than about 750 nanometers, canbe utilized to create the desired light scattering effect to improvedetection. These highly reflective particles are composed of a meanparticle size and density such that the ratio of the scattered orreflected light, as compared to the incident illumination (I_(s)/I_(o))described in the preceding mathematical relationship is maximized toabout 0.15 (15%) or greater, preferably about 0.5 (50%) or greater, andmost preferably about 0.90 (90%) or greater. It should be noted, howeverthat the maximum value obtainable is near about 1 (100%), and thatvalues within the range of about 0.90 (90%) to 1.0 (100%) are mostpreferred in accordance with the present invention.

The size for light scattering particles roughly spherical in shape areto have a mean diameter of less than 2 times the wavelength of theincident energy used for registration detection. The maximum particlesize should have a diameter of less than 2.5 times the wavelength of theincident energy used for registration detection. It is preferred thatthe mean particle diameter be from 0.5 to about 1.5 times the wavelengthof the incident energy used for registration detection. The particlesize distribution is preferably such that 95 percent of the particleshave diameters within 0.25 to 2.5 times the wavelength of the incidentenergy used for registration detection. Particles exceeding 3 times theincident wavelength will have little value for reflecting light eitheras a reflection device or as a blocking device.

Accordingly, safe materials with higher ratios of the scattered orreflected light, as comparted to the incident illumination (I_(s)/I_(o))are more favorable should they become available. This property can bemeasured directly, using a standard spectrophotometer covering thewavelength region of interest. The determination is made by measuringthe reflectance of a reflectance reference standard with predeterminedreflectance values near about 100%, correcting the reflectance spectrumto those values and measuring the test material. When using a ratioingspectrophotometer, the resultant reflectance or percent reflectance canbe displayed. The reflectance value is equivalent to the intensity ratioof scattering to incident light (I_(s)/I_(o)) for the measurementconditions used. FIG. 9 illustrates the case for a 1 micron wavelengthillumination in air, a 1 degree from normal angle of observation,particles with a refractive index of about 2.5, and a constant densityof particles per unit volume. Accordingly, the use of Equations C1 andC2 provide a computation of the dependency of the mean particle size tothe intensity ratio of scattered to incident light.

The scattering particles consisting of compounds described herein arecomposed of the appropriate calculated mean particle size. Theseparticles can be extruded into polymer structures and films at lowtemperatures (typically less than about 250° C.), or they can be addedto adhesives, printable latexes and print bases, or as ingredients tostandard paint bases for application to the desired component of thecomposite article. When reflective materials are added to films, theyare preferably selected to be stable at extrusion temperatures (e.g.,from about 70° C. to about 300° C.), and are efficacious and chemicallystable throughout the time of manufacture (up to and including about 15days beyond the storage and manufacturing use time). Greater stabilityis desirable but not required.

The reflective components are preferably substantially chemicallynon-reactive with polymers and polymer additives (such as polyolefinfilms and webs, or cellulose), or with adhesives or polymer coatings.The reflective components also are preferably selected so as not tobleed out of the structure over the manufacturing use period. The safetyof such components typically applies to human use in the relativeconcentrations required for efficient reflection enablement.

Particle density in the reflective substrate is preferably such that thelight reflection for the optically reflective material is at least oneorder of magnitude more highly reflective as compared to the surroundingmaterial; this is represented by at least 1.0 optical density unit whereoptical density (O.D._(R)) value for reflection is given as:O.D. _(R)=log₁₀(100/R _(p))where O.D._(R) is the optical density of a material at a specificwavelength, and R_(p) is the percent reflectance of the material at aspecific wavelength. The concentration of particles is evaluated fordifferent levels to empirically determine the optimum coverage to meetthese reflectance criteria.

In view of the foregoing, the precise concentrations of scatteringparticles required is typically determined by making a serial dilutionof scattering particles into the film and determining the optimumscattering as l_(s)/l_(o), which provides a precise estimate of particlesize and concentration useful for appropriate reflection levels. Whenthese measurements are combined with Equation D, below, an appropriatecontrast can be determined for any specific application. Theconcentration of scattering particles in or on a film structuretypically ranges from about 0.1% to about 20% by weight, preferably fromabout 0.5% to about 5%, and more preferably is less than about 2% byweight (e.g., from about 1% to less than about 2%).

The present invention provides for the use of scattering particleswithin a composite product for positioning of product components duringthe manufacture assembly. Suitable materials which can be used to addreflection properties to these registration structures include, forexample, low cost films containing titanum dioxide (TiO₂), bariumsulfate (BaSO₄), magnesium oxide (MgO), calcium carbonate (CaCO₃),porous and non-porous polytetrafluoroethylene (e.g., Teflon®) micronbeads, or polyolefins micro beads (such as polypropylene orpolyethylene) of appropriate size for light scattering.

Accordingly, using Equations C1 and C2, a preferred particle size can becalculated (see FIG. 9 for a nominal set of registration conditions).The refractive index of the materials comprising the particles ispreferably greater than about 1.5, more preferably greater than about 2,and most preferably greater than about 2.5. The high refractive indexinorganic materials are not water soluble, but are dispersible, and arepreferably added to film structures by extrusion into structures andfilms at low temperatures (e.g., less than about 250° C.). Inorganicmaterials and polymer micro beads, such as those conventionally used foraffinity chromatography, with a mean particle size or radius of about 1micron can be added to adhesives, printable latexes and print bases, oras ingredients to paint. The micro beads are suspended in a fixablemedium and can be sprayed or dipped onto the registration structures,then air dried to produce the desired light scattering effect.

For reflective light, the focus of the beam at the detector can be usedto assess z-directional positioning of a reflecting film layer orlayers. A single collimated light beam, or laser, is focused at anominal position provided a known beam diameter of the detector. Movingthe reflecting film position toward or away from the detector alters thesize of the beam at the detector. Moving the reflector toward thedetector reduces the beam diameter, while moving the reflector away fromthe detector enlarges the beam. This principle can be used to measure arelative z-axis position of a reflective surface. If two or morereflective surfaces are used, the difference in beam dimensions can beused to indicate the relative z-position between the two reflectivesurfaces.

Contrast is an important characteristic of registration and detection oftreated structures, and therefore is to be considered in selecting anideal reflective, absorptive, or transmissive material. Contrast isdefined as the ratio of the difference between the maximum illuminance(as I_(max) in units of lux) and the minimum illuminance (as I_(min)) ofa surface exhibiting two or more distinct levels of brightness (ordarkness) and the sum of the maximum and minimum illuminance. Theilluminance is determined using either back-lit or front-lit detectiongeometry, dependent upon the use of an absorber or reflectorapplication. If a power meter is unavailable, the values for l_(s)/l_(o)may be substituted for I in Equation D. Contrast is often specified fora typical interference-diffraction pattern, given the alternating lightand dark rings created by interference at a narrow slit. Contrast isdescribed by:Contrast=I _(max) −I _(min) /I _(max) +I _(min)  (D).Maximum contrast aids in optimizing registration (a contrast of about 1being large and about 0 being small); contrasts greater than about 0.2thus being preferred, with contrasts of greater than about 0.5 and 0.6being more preferred. This aspect of material and blocker selection isutilized in order to gain maximum contrast at a cost that is compatiblewith the specific manufacturing application. There are othercharacteristics which are also important in assessing the opticalquality of absorbers and reflectors, including clear definition of theconcept of illumination. Illumination is defined as the energy of light(E) striking a surface for a specific unit area per unit time. Thisdefinition is shown using the expression in Equation F:E=(I _(s) cos α)/d ²  (F)wherein

-   -   E is the illumination (or light energy) in lumens per mm²;    -   I_(s) is the source intensity in candlepower;    -   α is the angle between the source light rays and a unit vector        normal to the illuminated surface; and,    -   d is the distance, in mm, from the source to the illuminated        surface.

The illumination and angle of incidence and detection can change thecontrast ratios dramatically for use in registration. Thus, the optimummaterials for absorbing or reflection include those exhibiting themaximum contrast at a pre-specified set of measurement conditions,including wavelength of the source, sensitivity of the detector, angleof incidence and detection, illumination geometry, source intensity anddistance, and cost of absorbing or reflecting agents. These parametersare established by the cost and space requirements, as well as therestrictions of ambient lighting conditions.

The optimum set of materials, as well as illumination and detectionconditions, are established by calculating the optimum absorbing andreflection values for the materials, and then measuring contrast underthe anticipated measuring conditions. The use of this inventiontherefore provides for optimal optical contrast at a practical low costof implementation when compared to multilayered films and other opticalfilm technologies.

The absorbing and reflecting infrared blockers described herein forincorporation into one or more components of a composite product can beintroduced into a variety of components to improve detectability of thecomponent as compared to untreated components during infraredinspection. For example, blockers could be introduced into numerouscomponents including side panels, adhesives, surge materials, elasticstrands, superabsorbent polymer materials, waist elastic material, hookor loop or similar mechanical fastening devices, ink for graphics,attachment tapes, nonwoven sheets as utilized for outer covers orliners, and skin care ointments such as lotions or vitamin E. Oneskilled in the art will recognize that there are numerous othercomponents of composite articles that could be used in combination withthe blockers described herein in accordance with the infrared detectionsystem. As such, the above listing is simply meant to be illustrativeand not limiting.

As noted above and discussed herein, the infrared absorbing dyes andcompounds and reflecting materials described herein can be extruded intopolymer structures and films at low temperatures, typically less thanabout 250° C. Alternatively, they can be added to adhesives, printablelatexes and print bases, or as ingredients to paints. When added tofilms, they are preferably stable at extrusion temperatures from about70° C. to about 300° C., and must be efficacious and chemically stablethroughout the time of manufacture, typically up to and including about15 days beyond the storage and manufacturing use time. Additionally, theblocking compounds are generally selected to ensure: (i) they do notreact with the polymer, polymer additives, adhesives or polymer coatingswith which they are to be combined or mixed; and, (ii) they do not bleedout of the structures, or migrate across the surface of the structures,to be registered during the manufacturing use period. Finally, thesafety of such compounds generally applies to human use in the relativeconcentrations required for efficient optical blocking, based on theextinction coefficient of the blocker.

C. Register Inspection Using IR Blockers

Once the infrared blocker is introduced into or onto the desiredcomponent of the composite article, the component can be inspected asdescribed herein for its position relative to other components of thecomposite article. Specifically, infrared blockers can be introducedinto spunbond laminate side panels to determine the cross direction andmachine direction position of the side panels relative to the absorbentpad of the composite article. In another embodiment, infrared blockerscould be introduced into the ink used to create various graphics todetermine the position of the graphics relative to the absorbent pad. Ina still further embodiment, infrared blockers could be introduced into asurge layer to determine the surge layer position relative to theabsorbent pad. In a still further embodiment, infrared blockers could beintroduced into leg elastic strands to determine the position of the legelastic strands relative to the outer cover. In another embodiment,infrared blockers could be introduced into waist elastic to determinethe position of the waist elastic relative to the absorbent pad edge. Ina still further embodiment, infrared blockers could be introduced into ahook and loop type fastener to determine their position relative to thespun bond laminate edge prior to fastening; stated another way, theinspection of the placement of the hook and loop could be done while theproduct was still in web form.

In one embodiment of the present invention, instead of simplyintroducing the infrared blocker into only a single component of acomposite product for registration of the single blocked component, oneor more of the same or different infrared blockers can be introducedinto more than one component for registration. In this embodiment, theidentical infrared blocking compound can be introduced into or onto morethan one component of a composite product to allow registration fornumerous components and the determination of the position of eachblocked component relative to other unblocked components of thecomposite product. Alternatively, infrared blocking compounds havingdifferent absorption characteristics could be utilized in differentcomponents of the same composite product to produce differentialcontrast registrations for the blocked components of the compositeproduct. This embodiment would still allow the position of blockedcomponents of the composite product to be determined relative tounblocked components, and would further allow differentiation of blockedcomponents relative to each other.

In another embodiment of the present invention, the infrared blockersdescribed herein can be utilized on one or more components of acomposite article for quantitative analysis of the blocked component inthe composite product. For example, a superabsorbent polymer material,which is typically introduced into the absorbent core of a compositearticle to imbibe liquid in this region, could be treated, prior toincorporation into the absorbent core, with an infrared blockingcompound to block infrared light upon illumination. During manufactureof the composite article, the infrared detection system described hereincould capture an image of the absorbent core containing the blockedsuperabsorbent polymer material and determine the concentration ofsuperabsorbent polymer material based upon the amount of infrared lightthat was absorbed. A larger amount of superabsorbent material in theabsorbent core would result in increased absorption.

Similar to the quantitative analysis for the amount of superabsorbentpolymer material based on the absorption (or reflection) of infraredlight described above, infrared blockers could also be introduced into askin care ointment or adhesive material used on composite products andthe product registered using the infrared detection system describedherein. Based on the amount of absorption (or reflectance) of infraredlight, the concentration of ointment or adhesive material could bedetermined in a manner similar to that described above forsuperabsorbent polymer material. The image can also provide informationabout the distribution or application pattern of such components.

With further reference to FIG. 2, the image analyzer 208 may be, forexample, a programmable digital computer, and the comparator 210 may beimplemented in a variety of hardware and software configurations.Additionally, these various components of the system 200 may beimplemented singly or in combination without departing from the scope ofthe invention. For example, the comparator 210 and the image analyzer208 may be implemented within a single programmable computer. It shouldalso be understood that in any given embodiment of the invention, thecombination of infrared radiation source (including its intensity andwavelength(s)), infrared detector, radiation source/detector geometry,detector filter (if any), and infrared markers (if any) can be selectedas necessary to enhance detection of components of interest in acomposite article.

FIG. 4 illustrates another exemplary system 400 for implementing variousaspects of the present invention, including the process 100 of FIG. 1.The system of FIG. 4 is largely the same as that of FIG. 2, except thatthe radiation source 202 of FIG. 2 has been replaced with two radiationsources 402, 403 positioned adjacent the infrared detector on oppositesides thereof, and on a same side of the composite article as theinfrared detector. Thus, the system of FIG. 4 irradiates the compositearticle from a top side thereof, and produces an image from infraredradiation 406 received by the detector from the top side of thecomposite article (some of which may be reflected from intermediate orlower components of the composite article). This is in contrast to,e.g., irradiating the backside of the composite article with infraredradiation and producing an image from infrared radiation which passesentirely therethrough, as in one embodiment of the system of FIG. 2described above.

From the above description, it should be apparent that the presentinvention can be used to determine, among other things, whether one ormore components are properly positioned in a wide array of compositearticles. In fact, to the extent that such components do not inherentlyprovide an infrared response which readily permits their detection usingincident infrared (or other) radiation and infrared detectors, suchcomponents can be provided with a suitable infrared marker so as toimpart them with a desired response, as noted above.

While suited for a wide variety of applications, the present inventionis particularly useful in the production of absorbent articles, such asdisposable diapers, training pants, incontinence devices, sanitarynapkins, and the like. Thus, one exemplary application of the inventionfor detecting component positions will now be described with referenceto the disposable training pant 500 illustrated in FIG. 5, and withfurther reference to the exemplary detection system 200 of FIG. 2.Exemplary systems and processes for producing the training pant 500 aredescribed in international application PCT/US01/15803, the disclosure ofwhich is incorporated herein by reference.

In particular, FIG. 5 illustrates one end of a first side panel 502 ofthe training pant 500 joined with one end of a second side panel 504 viaa fastener component 506 (shown in phantom) previously bonded to thesecond side panel 504, and now disposed between the two side panels,with the first side panel 502 overlapping the second side panel 504 andthe fastener component 506. In this particular embodiment, the firstside panel 502 and the second side panel 504 are each formed from apigmented nonwoven material, such as a stretch bonded laminate (SBL),and the fastener component 506 is one of a hook component and a loopcomponent of a hook-and-loop fastener (e.g., a VELCRO brand fasteneravailable from Velcro Industries B.V.). A complementary fastenercomponent (not shown) is also bonded to an underside of the first panel502, and mates with the fastener component 506 bonded to the second sidepanel 504. Alternatively, other types of fasteners, includingsimilar-surface interlocking fasteners, may be used.

The portion of the training pant illustrated in FIG. 5 is supported byan infrared radiation apparatus 600, as shown in FIG. 6. The apparatus600 includes an infrared radiation source 602 and a diffuser 604. Thediffuser 604 supports a bottom side of the training pant 500, andrenders more uniform infrared radiation emanating from the infraredradiation source 602. In this example, the radiation source 602corresponds to the radiation source 202 of FIG. 2, and the training pant500 corresponds to the composite article 204. While only the uppercomponent of the infrared radiation apparatus 600 is illustrated in FIG.6, the apparatus 600 includes an equivalent lower component forirradiating an opposite side of the training pant 500 also not shown (topermit infrared detection of the training pant's opposite side usinganother or augmented system of the type shown in FIG. 2). In oneembodiment, the infrared radiation source 602 emits infrared radiationintermittently, and the infrared detector 205 is synchronized with theradiation source 602 so as to produce an image 700 of the training pantwhile it is irradiated with infrared radiation.

FIG. 7 illustrates the image 700 produced by the infrared detector 205of FIG. 2 from infrared radiation emanating from a top side of thetraining pant 500. Note that a least amount of radiation will emanatefrom that portion of the first side panel 502 which overlies thefastener component 506, since such radiation (if any) must pass throughthe second side panel 504, the fastener component 506, and the firstside panel 502, each of which at least partially inhibits infraredradiation from passing therethrough (e.g., by absorbing or reflectingsuch radiation). For this reason, the fastener component 506 appears inthe image 700 as a dark contrast region. A medium contrast region in theimage 700 corresponds to portions of the training pant where the firstside panel overlies the second side panel, but not the fastenercomponent. Light contrast regions in the image 700 correspond toportions of the training pant where the first side panel does notoverlie the second side panel. Thus, it should be apparent thatvariations in the image 700 (which, in this implementation, are contrastor grayscale variations) correspond to edge positions of the variouscomponents. Although only three contrast regions are shown in FIG. 7, itshould be understood that more or less contrast regions can be used inany given application of the invention.

Also illustrated in FIG. 7 are several arrows A-H which representsoftware “tools” employed by one preferred image analyzer 208 of FIG. 2for detecting variations in the image 700 which represent edge positionsof the first side panel 502, the second side panel 504, and the fastenercomponent 506. For example, tools A and B analyze the image 700 in thedirections shown to first detect contrast variations 702, 704 whichcorrespond to positions of the fastener component's edge 508, and thendetect contrast variations 706, 708 which correspond to the fastenercomponent's edge 510. Similarly, tools C and D analyze the image 700 todetect contrast variations 710, 712 which correspond to positions of thefirst side panel's edge 512, tools E and F analyze the image 700 todetect contrast variations 714, 716 which correspond to positions of thesecond side panel's edges 514, 516, and tools G and H analyze the image700 to detect variations 718, 720 which correspond to positions of thefirst side panel's edges 518, 520. Once identified by the imageanalyzer, the comparator of FIG. 2 compares these edge positions withpredetermined position data to thereby determine whether the first sidepanel, the second side panel, and the fastener component are properlypositioned in the training pant 500 in a fixed sense and/or relative toone another.

Note that in the particular implementation described immediately above,the fastener component 506 includes an infrared marker to increase aninfrared absorption characteristic of the fastener component 506, andthereby render it more susceptible to detection in the image 700.Alternatively, the intensity of the infrared radiation source may beincreased. However, a greater radiation intensity may render detectionof the first side panel's edge 512 more difficult. Thus, through use ofan infrared marker, in addition to appropriate selection of the infraredradiation source (including its intensity and wavelength range), theinfrared detector, and the radiation source/detector geometry, a systemcan be devised to readily detect a wide variety of composite articlecomponents, regardless of their position. In fact, the system 200 canalso be configured to detect positions of the second side panel's edge522 which underlies the first side panel, the second fastener component(not shown) noted above, and any other component of interest.

In one embodiment, incident radiation in the range of about 700-1200nanometers is preferred. This is because many existing inspectionsystems (previously used only for detecting visible and/or ultravioletradiation) can detect wavelengths of up to about 1200 nanometers, andcan thus be readily configured for implemented certain teachings of thepresent invention. Further, the inventors have determined that infraredradiation having a wavelength of about 940 nanometers is especially wellsuited for penetrating and detecting positions of pigmented nonwovenmaterials, including the blue and pink stretch bonded laminates commonlyemployed in fabricating disposable diapers, training pants, and thelike. Thus, the radiation source 602 shown in FIG. 6 preferably emitsradiation having a wavelength of about 940 nanometers (e.g., acommercially available infrared LED having a nominal value of 940nanometers). Additionally, the infrared detector used in theimplementation described above with references to FIGS. 5-7 preferablyincludes a filter for removing (i.e., blocking) radiation, such asambient and/or scattered radiation, having a wavelength of or belowabout 830 nanometers (e.g., a high pass filter having a nominal value ofabout 830 nanometers) including visible and ultraviolet radiation.Alternatively (or additionally), one or more shrouds may be employedaround the infrared detector to shield the detector from, e.g.,extraneous radiation sources (such as ceiling lights, natural light,etc.).

With further reference to FIG. 2, it should be apparent that the system200 shown therein is capable of detecting positions of not only stackedcomponents, but also overlapping components as well as nonoverlappingadjacent components. Further, the radiation source 202 need not be aninfrared radiation source in every application of the invention and, infact, is preferably not an infrared radiation source in certainembodiments, including one or more (but not all) embodiments where acomponent to be detected fluoresces in the infrared spectrum in responseto incident radiation outside of the infrared spectrum. The radiationsource may also emit multiple wavelengths or bands of wavelengths so asto cause multiple components which respond to different wavelengths ofincident radiation (due to use of infrared markers or otherwise) toexhibit their responses simultaneously, thus permitting theirsimultaneous detection. In this regard, the infrared detector mayinclude only a single infrared sensor or array of sensors capable ofdetecting multiple wavelengths or wavelength ranges, and thus multiplecomponents which exhibit different infrared responses to incidentradiation. Alternatively, the infrared detector may include multiple anddistinct infrared detectors, such as infrared cameras, and each of thesedetectors may be configured (via filters or otherwise) to detectdistinct wavelengths or wavelength ranges. Of course, multiple systemsof the types described herein may also be advantageously used incombination in any given application of the invention.

Additionally, a set of two or more discrete infrared detectors atoptimized observation angles can be configured with different band passfilters, illumination sources, and detection systems enablingsimultaneous real-time detection of different product components. Suchan approach may advantageously yield true z-directional spatialdiscrimination, in addition to two-dimensional (i.e., x and y) spatialdiscrimination. Thus, the individual detectors can be used to detect,for example, individual components each exhibiting a different infraredresponse to incident radiation (through use of infrared markers orotherwise) providing detailed x,y,z spatial detection and registrationof composite article components. A single infrared detector withmultiple wavelength capabilities can also be used to detect differentcomponents exhibiting infrared responses at different wavelengthsproviding detailed x and y spatial detection. A combination of thesesystems can provide optimum sensing for, among other things,registration detection based upon the number of components requiringregistration, the z-dimensional discrimination requirements, and costconcerns.

While one aspect of the invention, detecting a position of a componentin a composite article, has been described above, another aspect of theinvention includes detecting the presence (and thus the absence, whenapplicable) of a particular component in a composite article. Forexample, one exemplary process includes irradiating a composite articlewith radiation as the composite article moves relative to an infrareddetector. A component of the composite article, when present, is knownto exhibit a predefined response in response to incident radiation.Thus, the process further includes detecting the predefined response ofthe component in infrared radiation received from the irradiatedcomposite article to thereby detect the presence of the component. Asshould be apparent, when the particular component is present in theirradiated composite article, it will alter the article's response tothe infrared irradiation, such as by absorbing or reflecting infraredradiation at one or more particular wavelengths, or by fluorescing atone or more particular wavelengths. Thus, one or more variations willoccur in the detected infrared radiation (such as wavelength orintensity variations) which are indicative of the component's presence.In one embodiment, a single infrared sensor element is used as theinfrared detector to detect the infrared radiation received from theirradiated product as the product moves relative to the sensor element,where a high detector output level indicates a presence of the componentand a low detector output level indicates an absence of the component(or vice versa).

The infrared detector may also produce an image from infrared radiationreceived from the irradiated composite article. In such a case, theprocess would include identifying the predefined response of thecomponent in the produced image (e.g., by detecting variations, such ascontrast variations, indicative of the component's presence) to therebydetect the presence of that component.

While an exemplary process for detecting a presence of a singlecomponent has been described above, it should be readily apparent thatmore than one and in fact many different components may be similarlydetected, including components which include infrared markers for thepurpose of providing or enhancing their infrared responses to incidentradiation.

According to another aspect of the invention, the distribution of aplurality of components, each having a predefined response to incidentradiation (due to use of infrared markers or otherwise), in a compositearticle may be readily determined. One exemplary process includesirradiating the composite article with the incident radiation, andproducing an image from infrared radiation received from the compositearticle, where the image includes a pattern, formed by the predefinedresponse of the composite articles, which corresponds to theirdistribution. This pattern is then compared to reference data (such asone or more predefined patterns corresponding to ideal or acceptabledistributions) to determine whether the composite articles are properlydistributed in the composite article. In one embodiment, the comparingincludes performing a pattern matching function using a suitablyconfigured computer device. This aspect of the invention is particularlyuseful in, for example, determining the distribution of absorbentparticles, adhesives, and ointments used in fabrication of a disposableabsorbent article.

The distribution of components in a composite article, each having apredefined response to incident radiation, may also be determined byirradiating the composite article with incident radiation, measuring alevel of infrared radiation received from each of a plurality of regionsof the irradiated composite article, and comparing the level of infraredradiation measured for each of the plurality of regions with referencedata to thereby determine whether the components are properlydistributed in the composite article. One or more infrared detectors maybe provided for measuring the infrared radiation received from eachregion of the composite article. In one embodiment, an infrared detectoris used to produce a two dimensional image from infrared radiationreceived from the composite article. The image is then analyzed toidentify therein the regions of the composite article mentioned above,and to determine the grayscale level of each region. Thus, if thecomposite article is irradiated with infrared radiation, and thecomponents of the composite article each inhibit at least some infraredlight from passing therethrough, then darker portions of the producedimage will correspond to regions of the composite article whererelatively more of the components are present. Thus, by comparing thedetermined grayscale levels with reference data, the distribution of thecomponents in the composite article may be readily determined orapproximated. In one application, this process is used to determinewhether superabsorbent particles are properly distributed in adisposable absorbent product, such as a diaper.

In a similar application of the present invention, the concentration(i.e., quantity) of a plurality of components, each having a predefinedresponse to incident radiation (due to use of infrared markers orotherwise), in a composite article may be readily determined. Oneexemplary process includes irradiating the composite article with theincident radiation, and then measuring the predefined response of theplurality of components (e.g., the intensity of infrared radiationreceived from the irradiated component, such as the intensity at one ormore particular wavelengths). The measured response is then comparedwith reference data to determine or at least approximate the quantity ofthe components in the composite article. This aspect of the invention isalso useful in, for example, determining the quantity of absorbentparticles, adhesives, and ointments used in fabricating a disposableabsorbent article.

As used herein, “infrared radiation source” refers to any device capableof emitting radiation in the infrared spectrum (i.e., radiation having awavelength between about 700 nanometers and one millimeter), regardlessof whether it also emits radiation in other spectrums. Some examples ofinfrared radiation sources suitable for certain embodiments of thepresent invention include infrared LEDs, mercury vapor lamps, argonlamps, arc lamps, lasers, etc. In contrast, “radiation source” refers toany device capable of emitting radiation in any spectrum, which may ormay not include the infrared spectrum.

“Infrared detector” refers to any device having one or more sensorelements (including a matrix of sensor elements) capable of sensinginfrared radiation, regardless of whether such device can also senseradiation in other spectrums. Thus included in this definition areexisting vision inspection cameras which are capable of detecting notonly visible and ultraviolet light, but also infrared radiation ofwavelengths up to about 1200 nanometers (as noted above), line scancameras capable of building an image one line at a time from infraredradiation received from an article as the article is moved relativethereto, as well as any other device capable of producing a one, two orthree dimensional image from received infrared radiation including,without limitation, a charge coupled device (“CCD”).

As alluded to above, any infrared detector used in the present invention(as well as any composite article to be detected thereby) may beprovided with a filter for filtering unwanted wavelengths, includingthose in the infrared and/or other spectrums, as desired. Such filtersinclude low-pass filters which remove radiation above a predefinedwavelength, high-pass filters which remove radiation below a predefinedwavelength, band-pass filters which remove all radiation except thathaving a wavelength within a predefined range, and combinations thereof.One or more of these filters may be useful for removing ambient,scattered, or even incident radiation (such as when detecting componentswhich fluoresce at different wavelengths than the incident radiation) inany given application of the invention.

The infrared and other radiation sources described herein, as well asthe infrared detectors, may include fiber optic devices in variousapplications of the invention, such as to precisely irradiate or detectradiation from a specific component or region in a composite article.

Additionally, it should be understood that as used herein, the term“component” shall include not only discrete objects, but also objectsyet to be formed into discrete objects (e.g., objects yet to be severedinto discrete objects from a continuous sheet or web of material),particles (e.g., superabsorbent particles or polymers), adhesives,lotions, ointments, and other substances, as well as portions orcharacteristics of any such components including, for example, foldlines, bond lines (e.g., ultrasonic bond lines), bonded or adheredregions, and registration marks applied to or about components forsubsequent detection during a manufacturing or inspection process.Indeed, the teachings of the invention can be used to detect thepresence, position, concentration, and distribution of chemical,physical, optical, and component structural properties for any compositearticle under observation.

When introducing elements or features of the present invention or thepreferred embodiments thereof, the articles “a”, “an”, “the” and “said”are intended to mean that there are one or more such elements orfeatures. The terms “comprising”, “including” and “having” are intendedto be inclusive and mean there may be additional elements or featuresother than those listed.

As various changes could be made in the above embodiments withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1. A process of detecting whether one or more components are properlypositioned in a composite article, the process comprising: irradiatingthe composite article with infrared radiation; producing an image frominfrared radiation received from the irradiated composite article;identifying a position of a first variation in the produced imagecorresponding to an underlying edge of a first component in thecomposite article, said underlying edge overlapped by at least a portionof a second component which is substantially opaque to or which scattersvisible and/or ultraviolet light; and comparing the identified positionwith predetermined position data to thereby determine whether the firstcomponent is properly positioned in the composite article.
 2. Theprocess of claim 1 wherein the identified position is a relativeposition, and wherein comparing includes comparing the identifiedrelative position to predetermined relative position data to therebydetermine whether the first component is properly positioned in thecomposite article.
 3. The process of claim 2 wherein identifyingincludes identifying a position of a second variation in the producedimage corresponding to an edge position of a second component in thecomposite article, and identifying the position of the first variationin the produced image relative to the position of the second variation.4. The process of claim 3 wherein the composite article is a disposableabsorbent article.
 5. The process of claim 1 wherein irradiatingincludes irradiating a first side of the composite article with theinfrared radiation, and wherein producing includes producing the imagefrom infrared radiation received from a second side of the irradiatedcomposite article opposite the first side.
 6. A composite articleprocessed using the process of claim
 1. 7. The composite article ofclaim 6 wherein the composite article is a disposable absorbent article.8. A process of detecting whether components of a composite article areproperly positioned with respect to one another, each component at leastpartially inhibiting infrared radiation from passing therethrough, theprocess comprising: irradiating the composite article with infraredradiation; producing an image from infrared radiation received from theirradiated composite article; identifying positions of variations in theproduced image, including identifying a position of a first variation inthe produced image corresponding to an underlying edge of a firstcomponent in the composite article, said underlying edge overlapped byat least a portion of a second component which is substantially opaqueto or which scatters visible and/or ultraviolet light, and identifying aposition of a second variation in the produced image corresponding to anedge position of the second component in the composite article; andcomparing at least one of the identified positions with predeterminedposition data to thereby determine whether the first component and thesecond component are properly positioned with respect to one another inthe composite article.
 9. The process of claim 8 wherein identifyingincludes identifying the position of the first variation in the producedimage relative to the position of the second variation, and whereincomparing includes comparing the identified relative position of thefirst variation with predetermined relative position data to therebydetermine whether the first component and the second component areproperly positioned with respect to one another in the compositearticle.
 10. The process of claim 8 wherein the composite articleincludes at least the first component, the second component, and a thirdcomponent, wherein identifying includes identifying a position of athird variation in the produced image corresponding to an edge positionof the third component in the composite article, and wherein comparingincludes comparing at least two of the identified positions withpredetermined position data to thereby determine whether the firstcomponent, the second component, and the third component are properlypositioned with respect to one another in the composite article.
 11. Theprocess of claim 10 wherein the second component is disposed between thefirst component and the third component.
 12. The process of claim 8wherein the first variation and the second variation are contrastvariations.
 13. The process of claim 8 wherein the image is a stilltwo-dimensional image.
 14. The process of claim 8 wherein the compositearticle is a disposable absorbent article.
 15. The process of claim 14wherein the second component is a fastener component.
 16. The process ofclaim 15 wherein the fastener component is one of a hook component and aloop component of a hook-and-loop fastener.
 17. The process of claim 14wherein irradiating includes irradiating the composite article withinfrared light having a wavelength in a range of about 700-1200nanometers.
 18. The process of claim 17 wherein irradiating includesirradiating the composite article with infrared light having awavelength of about 940 nanometers.
 19. The process of claim 8 whereinirradiating includes irradiating a first side of the composite articlewith the infrared radiation, and wherein producing includes producingthe image from infrared radiation received from a second side of theirradiated composite article opposite the first side.
 20. The process ofclaim 8 wherein irradiating includes irradiating one side of thecomposite article with the infrared radiation, and wherein producingincludes producing the image from infrared radiation received from saidone side of the irradiated composite article.
 21. A composite articleprocessed using the process of claim
 8. 22. The composite article ofclaim 21 wherein the composite article is a disposable absorbentarticle.
 23. A system for detecting whether one or more components areproperly positioned in a composite article, the system comprising: aninfrared radiation source for irradiating the composite article withinfrared radiation; an infrared detector for producing an image frominfrared radiation received from one side of the irradiated compositearticle; an image analyzer operatively connected to the infrareddetector for identifying a position of a first variation in the producedimage corresponding to an underlying edge of a first component in thecomposite article, said underlying edge overlapped by at least a portionof a second component which is substantially opaque to or which scattersvisible and/or ultraviolet light; and a comparator operatively connectedto the image analyzer for comparing the identified position withpredetermined position data to thereby determine whether the firstcomponent is properly positioned in the composite article.
 24. Thesystem of claim 23 wherein the image analyzer is configured foridentifying the position of the first variation as a relative position,and wherein the comparator is configured for comparing the identifiedrelative position to predetermined relative position data to therebydetermine whether the first component is properly positioned in thecomposite article.
 25. The system of claim 24 wherein the image analyzeris configured for identifying a position of a second variation in theproduced image corresponding to an edge position of the second componentin the composite article, and for identifying the position of the firstvariation in the produced image relative to the position of the secondvariation.
 26. The system of claim 23 wherein the infrared radiationsource and the infrared detector are each positioned on said one side ofthe composite article.
 27. The system of claim 23 wherein the infrareddetector is positioned on said one side of the composite article and theinfrared radiation source is positioned on an opposite side of thecomposite article.
 28. The system of claim 23 wherein the compositearticle includes a third component, and wherein the second component isdisposed between the first component and the third component.
 29. Thesystem of claim 23 wherein the image analyzer comprises a programmabledigital computer.
 30. A composite article processed using the system ofclaim
 23. 31. The composite article of claim 30 wherein the compositearticle is a disposable absorbent article.